Modal Energy Research Articles

Seismic response and damage model analysis of rocky slopes with weak interlayers

Abstract A large-scale shaking table test of an anti-dip rock slope with a weak interlayer is conducted based on the Hongshiyan landslide induced by the Ludian earthquake. The dynamic failure mode energy damage identification method is analyzed using the Hilbert–Huang transformation and marginal spectrum theory. The result shows that the weak interlayer under horizontal loading amplifies the 5–10 and 25–30 Hz frequency signal and attenuates the 15–20 Hz signal. Within the hard rock, it amplifies the 5–15 Hz frequency signal and attenuates the 20–30 Hz signal. Under vertical loading, both weak interlayer and hard rock have an amplification effect on 5–30 Hz signal, and the amplification effect of weak interlayer is more significant. The horizontal seismic wave slope damage process can be divided into two stages: internal damage and obvious failure. When the horizontal seismic input amplitude reaches 0.2–0.3 g, internal damage occurs in the slope. The slope damage is primarily concentrated below two-third of the hard rock height and primarily in the shallow and surface regions of the slope. An input amplitude in the range of 0.4–0.5 g corresponds to the obvious failure stage. At this time, the slope first undergoes an obvious rupture in the rock above the weak layer; this rupture then extends upward to the top of the slope. Marginal spectral analysis results are consistent with the field model slope macroscopic rupture phenomenon.

Chalcogenide dual-core all-solid anti-resonant fiber polarization beam splitter operating at 3 μm band

Abstract For the first time, we proposed a polarization beam splitter (PBS) designed based on chalcogenide dual-core all-solid anti-resonance fiber (AS-ARF) and simulated it numerically using the finite element method (FEM). Two large cladding tubes are introduced to divide the fiber core into fiber cores A and B. Mode coupling and energy exchange between the two fiber cores are enabled through the gap g between the two large cladding tubes. By adjusting the structural parameters of the AS-ARF, polarization beam-splitting ability and single-mode characteristics can be obtained. The influence of the position of the nested tube within the large cladding tube on the performance of the PBS is further investigated. The numerical results show that the beam-splitting lengths of the two proposed PBSs are 9.5 cm and 8.2 cm, respectively, and the polarization extinction ratios (PERs) are −55.98 dB and −41.35 dB at 3 μm. In the wavelength range from 2.98 μm to 3.03 μm, both PBSs can simultaneously achieve polarization beam-splitting and single-mode characteristics. The proposed chalcogenide-based dual-core AS-ARF is a suitable candidate for PBS in the mid-infrared 3 μm band.

Impact of Key DMD Parameters on Modal Analysis of High-Reynolds-Number Flow Around an Idealized Ground Vehicle

This study provides a detailed analysis of the convergence criteria for dynamic mode decomposition (DMD) parameters, with a focus on sampling frequency and period in high-Reynolds-number flows. The analysis is based on flow over an idealized road vehicle, the Ahmed body (Re=7.7×105), using computational fluid dynamics (CFD) data from improved delayed detached eddy simulation (IDDES). The pressure and velocity spectrum analysis validated IDDES’s ability to capture system dynamics, consistent with existing studies. For a comprehensive understanding of the contributions of different components of the circle, the Ahmed body was divided into three regions: (a) front; (b) side, lower, and upper surfaces; and (c) rear fascia. Both pressure and skin-friction drag were analyzed in terms of frequency spectra and cumulative energy. Key findings show that a 90% contribution to the pressure drag comes from modes with a frequency of less than 26 Hz (St = 0.187), while the friction drag requires 84 Hz (St = 0.604) for similar energy capture. This study highlights the significance of accounting for intermittency and non-stationary behavior in turbulent flows for DMD convergence. A minimum of 3000 snapshots is necessary for the convergence of DMD eigenvalues, and sampling frequency ratios between 5 and 10 are needed to achieve a reconstruction error of less than 1%. The sampling period’s convergence showed that T*=250 (equivalent to 20 cycles of the slowest coherent structures) stabilizes coherent mode shapes and energy levels. Beyond this, DMD may become unstable. Additionally, mean subtraction was found to improve DMD stability. These results offer critical insights into the effective application of DMD in analyzing complex vehicle flow fields.

Flow control of blade-end oscillating jets on corner separation in a high-load compressor cascade

Based on unsteady numerical simulation, the feasibility of utilizing a fluid oscillator to generate oscillating jets for relieving the compressor cascade's corner separation was investigated. First, at design incidence angle, the optimal jet position is located where corner separation is not fully developed (74% axial chord length). Jets at more upstream and downstream positions are less effective due to premature dissipation of jet effects and the occurrence of high corner losses, respectively. The effectiveness of separation control through jet injection increases with higher jet mass flow rates, and the scheme with 0.66% relative jet flow rate exhibits a wide effective jet position range. However, excessively low jet flow rates are sensitive to jet position selection, while excessively high jet flow rates lead to significant mixing losses, resulting in high overall field losses and reduced engineering applicability. Second, the optimal jet scheme remains consistent at both design and high incidence angles and exhibits effective control at other off-design incidence angles. Finally, the oscillating jet suppresses the spanwise development of wall vortex and passage vortex within the blade passage by injecting high-momentum flow. Moreover, proper orthogonal decomposition analysis indicates that the oscillating jet redistributes the modal energy of the original flow field, exciting the vortex structures into high-frequency, small-scale oscillations at the jet frequency. Meanwhile, the oscillating jet primarily facilitates momentum exchange through strong mixing with passage vortex, wall vortex, and concentrated separation vortex, ultimately mitigating corner separation and reducing corner loss.

Improving Indonesia's Tsunami Early Warning: Part I: Developing Synthetic Tsunami Scenarios and Initial Deployment

Indonesia's Java subduction zone has triggered devastating tsunamis, emphasizing the need for a robust Tsunami Early Warning System, specifically for Southern Java, Bali, and Nusa Tenggara. With only six Ocean Bottom Pressure Gauges (OBPGs) currently monitoring tsunami propagation in the deep sea, optimized future sensor deployment is crucial. This paper, the first in a two-part series, proposes new observation networks to enhance tsunami early warning system. Our methodology involves developing synthetic stochastic-slip earthquake-induced tsunami simulations, delineating tsunami lead times, and applying empirical orthogonal functions (EOF) to determine spatial modal energy. We also assess the reliability of spacing and bathymetry for potential sensor locations. Our analysis reveals potential locations for additional OBPGs across the area. The proposed network consists of 42 additional sensors, demonstrating the potential for earlier warnings. These findings lay the groundwork for the second part of our series, where we will develop advanced forecasting models incorporating deep learning techniques based on the proposed location and further optimize sensor locations with the novel approach of hybrid optimizer and deep learning model. By establishing an improved observation network, this study contributes to more effective tsunami early warning systems in Indonesia, potentially mitigating the impact of future events on coastal communities.

Analysis of plasmon modes in Bi2Se3/graphene heterostructures via electron energy loss spectroscopy

Topological Insulators (TIs) are promising platforms for Quantum Technology due to their topologically protected surface states (TSS). Plasmonic excitations in TIs are especially interesting both as a method of characterisation for TI heterostructures, and as potential routes to couple optical and spin signals in low-loss devices. Since the electrical properties of the TI surface are critical, tuning TI surfaces is a vital step in developing TI structures that can be applied in real world plasmonic devices. Here, we present a study of Bi2Se3/graphene heterostructures, prepared using a low-cost transfer method that reliably produces mono-layer graphene coatings on Bi2Se3 flakes. Using both Raman spectroscopy and electron energy loss spectroscopy (EELS), we show that the graphene layer redshifts the energy of the plasmon mode in Bi2Se3, creating a distinct surface plasmon that differs significantly from the behaviour of a TI-trivial insulator boundary. We demonstrate that this is likely due to band-bending and electron transfer between the TI surface and the graphene layer. Based on these results, we outline how graphene overlayers can be used to create tuneable, stable plasmonic materials based on topological insulators.

Study on uniaxial compression mechanical properties of 3D printed columnar joint test blocks

The columnar joint skeleton of 3D printed Acrylonitrile Butadiene Styrene (ABS) material, the skeleton of cement mortar and ultraviolet aging treatment are combined to pour the columnar joint rock mass (CJRM) test block. The strength, deformation, energy and failure modes of the specimens with different dip angles were analyzed by uniaxial compression test. The influence of joint skeleton on the strength of the test block was analyzed. The effect of aging time on ABS parameters was evaluated. The results show that the uniaxial compressive strength and elastic modulus are ' U ' type with the increase of dip angle, the elastic strain energy is ' V ' type, and the dip angle of 45° is the minimum value. The four failure modes are: shear failure, splitting failure, shear tensile mixed failure, shear splitting mixed failure. The anisotropy of CJRM is extremely high. The skeleton reduces the strength and elastic modulus of the solid test block, and has the greatest influence on the strength of the test block with dip angle of 75°. With the increase of aging time, the strength and deformation parameters of ABS decreased, and the yellowness index and infrared spectrum peak area increased.

High-Performance Shear Mode Ultrasonic Transducer Operating at Ultrahigh Temperature Fabricated with Bi12SiO20 Piezoelectric Crystal.

Shear mode ultrasonic waves are in high demand for structural health monitoring (SHM) applications owing to their nondispersive characteristics, singular mode, and minimal energy loss, especially in harsh environments. However, the generation and detection of a pure shear wave using conventional piezoelectric materials present substantial challenges because of their complex piezoelectric response, involving multiple modes. Herein, we introduce a high-quality piezoelectric crystal Bi12SiO20 (BSO), exhibiting a robust piezoelectric response (d14 = 45.1 pC/N) and a pure vibration mode. Thereafter, we developed a BSO-based shear mode ultrasonic transducer and conducted finite element simulations and experiments. Results indicated that the proposed transducer excels in exciting and receiving pure shear waves with a high signal-to-noise ratio across a wide operating frequency range. Remarkably, the proposed transducer demonstrates efficacy ranging from 25 to 800 °C, which exhibits an exceptionally high operating temperature. These excellent attributes, coupled with cost-effectiveness, render this crystal highly promising for practical SHM applications.

Sub-Alfvénic Turbulence: Magnetic-to-kinetic Energy Ratio, Modification of Weak Cascade, and Implications for Magnetic Field Strength Measurements

We study the properties of sub-Alfvénic magnetohydrodynamic (MHD) turbulence, i.e., turbulence with Alfvén mach number M A = V L /V A < 1, where V L is the velocity at the injection scale and V A is the Alfvén velocity. We demonstrate that MHD turbulence can have different properties, depending on whether it is driven by velocity or magnetic fluctuations. If the turbulence is driven by isotropic bulk forces acting upon the fluid, i.e., is velocity driven, in an incompressible conducting fluid we predict that the kinetic energy is MA−2 times larger than the energy of magnetic fluctuations. This effect arises from the long parallel wavelength tail of the forcing, which excites modes with k ∥/k ⊥ < M A. We also predict that as the MHD turbulent cascade reaches the strong regime, the energy of slow modes exceeds the energy of Alfvén modes by a factor MA−1 . These effects are absent if the turbulence is driven through magnetic fluctuations at the injection scale. We confirm our predictions with numerical simulations. Since the assumption of magnetic and kinetic energy equipartition is at the core of the Davis–Chandrasekhar–Fermi (DCF) approach to measuring magnetic field strength in sub-Alfvénic turbulence, we conclude that the DCF technique is not universally applicable. In particular, we suggest that the dynamical excitation of long azimuthal wavelength modes in the galactic disk may compromise the use of the DCF technique. We discuss alternative expressions that can be used to obtain magnetic field strength from observations and consider ways of distinguishing the cases of velocity and magnetically driven turbulence using observational data.

Quantum valley Hall effect-based topological boundaries for frequency-dependent and -independent mode energy profiles

Topological artificial crystals can exhibit one-way wave-propagation along the boundary with the wave being localized perpendicular to the boundary. The control of localization of such topological wave propagation is of great importance for enhancing coupling or avoiding unwanted coupling among neighboring boundaries toward topological integrated circuits. However, the effect of the geometry of topological boundaries on localization properties is not yet fully clear. Here, we experimentally and numerically demonstrate valley-topological transport on representative valley-topological boundaries with micro-electro-mechanical systems. We show that the zigzag and bridge boundaries, which have highly efficient wave transport, exhibit frequency independent and dependent wave localization, respectively. A simple analytic model is presented to capture the different behaviors of the two boundaries observed in the experiments. Our results provide opportunities to engineer frequency responses in topological circuits including frequency selective couplers through proper selection of boundary geometries.

High-Order Theory Approach for Debonded Sandwich Panels—Part I: Formulation and Displacement Fields

Abstract A high-order theory is developed to model asymmetric sandwich panels with face/core debonds and to provide a solution for the energy release rate and mode mixty. This new theory is a novel re-formulation of the extended high-order sandwich panel theory (EHSAPT), in which faces and core were originally considered to be perfectly bonded. In the new formulation, a sandwich panel with an interfacial debond can be divided into three parts, namely, the debonded part, the substrate part, and the base part. A new high-order displacement pattern is developed to describe the core’s deformation in the substrate part, and it is compatible with the displacement field of the core in the base part. In addition, capturing the high-order shear deformation of the core, this new theory is able to take the transverse compressibility and axial rigidity of the core into account. In this Part I of this two-part research, we focus on the formulation and the displacement field. In Part II, the fracture parameters, namely, the energy release rate and the mode mixity will be addressed. Accordingly, in this paper, results for the deformation of the debonded panel are produced and compared with the ones given by the finite element method with a very fine mesh. The accuracy is proven for a wide range of core materials and for a wide range of debond lengths.

High-Order Theory Approach for Debonded Sandwich Panels—Part II: Energy Release Rate and Mode Mixity

Abstract A novel re-formulation of the extended high-order sandwich panel theory (EHSAPT) for the case of a face/core debond was done in Part I of this two-part series of papers. This high-order theory is capable of including not only the transverse shear but also the transverse compressibility and axial rigidity of the core. In this Part II paper, a closed-form expression for the energy release rate is derived in terms of the equivalent resultant forces and displacements at the two edge sections. Together with the crack surface displacement method, the mode mixity is determined from the displacement field. Benefiting from the accurate displacement field given by the proposed theory, this paper presents a self-contained approach for the mode mixity that is free of parameters that need to be determined via additional numerical simulations (i.e., no extrapolation needed). Results are compared with the ones given by the classical theory in the literature and the ones given by the finite element method with a very fine mesh. The accuracy is proven for a wide range of core materials from the stiffer cores to the very compliant ones, and for a wide range of debond lengths.

Highly Efficient and Linearly Polarized Light Emission of Micro-LED Integrated with Double-Functional Meta-Grating.

Linearly polarized micro light-emitting diodes (LP-Micro-LEDs) exhibit exceptional potential across diverse fields. The existing methods to introduce polarization to initially unpolarized Micro-LEDs and to further enhance the degree of polarization are, however, at the expense of low luminous efficiency. We fabricated a GaN-based blue Micro-LED integrated with a Al nanograting and a specially designed Ag/GaN meta-grating, which overcomes the dilemma between the luminous efficiency and polarization degree by simultaneously introducing the effects of mode selection and energy recycling. The fabricated LP-Micro-LED achieves an average polarization extinction ratio (ER) of 21.92 dB within ±60°, showing a 2.04-fold increase in efficiency and a 1.32-fold increase in ER compared to the Ag reflector design. This approach opens the way toward the next generation of high-efficiency and low-cost optoelectronic devices in encryption, displays, optical communication, and medicine.

Shaping Quantum Noise through Cascaded Nonlinear Processes in a Dissipation-Engineered Multimode Cavity

Multimode quantum light is enticing for several applications, spanning imaging, spectroscopy, communication, and more. Parametric nonlinear processes have been vital in realizing squeezed and other quantum states of light. However, most work exploiting these processes has focused on generating multimode squeezed vacua and squeezing in mode superpositions (supermodes). Bright squeezing in multiple discrete frequency modes, if realized, could unlock novel applications in quantum-enhanced spectroscopy and optical quantum computing. Here, we show how dissipation engineering of a multimode nonlinear cavity with cascaded three-wave-mixing processes allows us to shape above-threshold frequency combs that feature strong single-mode output amplitude noise squeezing over 10 dB below the shot-noise limit, tunable across the comb. In addition, we demonstrate squeezing for multiple discrete frequency modes above threshold. This bright squeezing arises from enhancement of the (noiseless) nonlinear rate relative to decay rates in the system due to the cascaded generation of photons in a single idler “bath” mode. A natural consequence of the strong nonlinear coupling in our system is the creation of an effective cavity in the synthetic frequency dimension that sustains Bloch oscillations in the modal energy distribution. Bloch mode engineering could provide an opportunity to better control nonlinear energy flow in the synthetic frequency dimension, with exciting applications in quantum random walks and topological photonics. Lastly, we show evidence of long-range correlations in amplitude noise between discrete frequency modes, enabling long-range entanglement in a synthetic frequency dimension and providing a new resource for quantum communication. Published by the American Physical Society 2024

Modal energy equivalence method for calculating amplitude-dependent viscous damping of distributed stick–slip systems

Modal energy equivalence method for calculating amplitude-dependent viscous damping of distributed stick–slip systems

Waves and non-propagating modes in stratified MHD turbulence subject to a weak mean magnetic field

In this study we consider a freely decaying, stably stratified homogeneous magnetohydrodynamic turbulent plasma with a weak vertical background magnetic field ( $\boldsymbol {B}_0=B_0\hat {\boldsymbol {z}}),$ aligned with the density gradient of strength $N$ (i.e. Brunt–Väisälä frequency). Both linear theory and direct numerical simulations (DNS) are used to analyse the flow dynamics for a Boussinesq fluid with unitary magnetic and thermal Prandtl numbers. We implemented a normal mode decomposition emphasizing different types of motions depending on whether both the Froude $F_r$ and Alfvén–Mach $M$ numbers are small or only $F_r$ is small but $M$ is finite. In the former case, there is a non-propagating (NP) mode and fast modes: Alfvén waves with frequency $\omega _a$ and magnetogravity waves with frequency $\omega _{ag}$ . In the latter case, there are fast gravity waves with frequency $\omega _g$ and slow modes: NP mode and slow Alfvén waves. The numerical simulations carried out are started from initial isotropic conditions with zero initial magnetic and density fluctuations, so that the initial energy of the NP mode is strictly zero, for $0&lt; B_0/(L_iN)\leqslant 0.12$ and a weak mean magnetic field ( $B_0=0.2$ or $B_0=0.4),$ where $L_i$ denotes the isotropic integral length scale. The DNS results indicate a weak turbulence regime for which $F_r$ is small and $M$ is finite. It is found that the vertical magnetic energy as well as the energy of the NP mode are drastically reduced as $N$ increases, while there is instead a forward cascade even for the magnetic field. The contribution coming from the energy of fast (gravity) waves does not exceed $50\,\%,$ while that coming from the energy of the NP mode does not exceed $10\,\%.$ Vertical motions are more affected by the effect of stratification than by the effect of the mean magnetic field, while it is the opposite for horizontal motions. We show that the spectrum of slow (Alfvén) waves and fast (gravity) waves tends to follow the power law $k_\perp ^{-3}$ for a wide range of time, $3&lt; t&lt;20$ . At high vertical (or horizontal) wavenumbers, the main contribution to total energy comes from the energy of slow Alfvén waves. At large and intermediate horizontal (or vertical) scales, the spectra of the energy of NP mode exhibit a flat shape.

Energy crisis of 2021–2022 as a harbinger of a change in the global energy system

The energy mode concept, has been characterized. Energy patterns types, history of their formation and development have been summarized. The prerequisites for forming a new energy mode based on the increasing share of renewable energy sources and hydrogen raw materials in the energy production structure have been highlighted. The change of the energy structure will take place in the coming decades. The following scientific methods of research were used in the paper: literature analysis and analysis of statistical data. Data for the period from 1965 to 2022 were used. The purpose of the study is to identify the role of the energy crisis of 2021–2022 as a factor contributing to a new energy structure formation that will be implemented in the coming decades. The subject of the study is to analyze and evaluate the change of the energy pattern in the international energy market, and the object of the study is the world energy market.

Influence of cavity crystal defects on the thermal ecomposition mechanism of NTO

Abstract The impact of cavity crystal defects on the thermal decomposition process of 3-nitro-1,2,4-triazol-5-one (NTO) was examined utilizing the reaction molecular dynamics method. A perfect crystal model of NTO and crystal models with cavity defects at concentrations of 0.78%, 1.17%, 2.34%, 3.13%, and 5.10% were constructed, and the potential energy and product changes in the isothermal mode at 2500 K were calculated. The impact of cavity defects was analyzed for the initial reaction stages, and the thermal decomposition reaction rate of 2500 K was calculated. The results demonstrate that at 2500 K, the complex reaction of NTO is enhanced, with the denitration reaction emerging as the dominant initial reaction type, followed by the ring-breaking reaction, and the proton transfer reaction occurring with a lower frequency. The principal intermediate products were CO2, NO2, HON, etc. The final products included N2, N4, H2O, HO2, and O2. In the range of 0.78% to 2.34% cavity content, the initial chemical reaction rate of NTO exhibited a slowing down trend with the increase of hole concentration. A collapse in the crystal structure accompanied this. Conversely, an acceleration was observed in the initial chemical reaction rate of NTO when the cavity concentration exceeded 2.34%.

Particle flow simulation of fracture responses and anchoring mechanisms of cemented materials subjected to static-dynamic combined loads

This study aims to reveal the evolution of energy, cracks, force chain, and ultimate failure modes of cemented gangue backfill materials subjected to static-dynamic combined loads, as well as the reinforcement mechanisms of pre-tightening bolts on mechanical performance and progressive damage. The particle flow models with various fractal dimensions (D) of particle size distribution were established, and irreversible damage accumulation during dynamic loading was achieved through a nonlinear parallel-bonded stress corrosion model. The simulation results show that, compared to uniaxial compression, the energy release lag at peak strength is eliminated under static-dynamic combined loading, and the brittle failure feature becomes more pronounced. The filling effect of fine aggregates optimizes the uniformity of internal stress distribution, with the peak parallel bond strain energy increasing by 9.60%, 8.42%, and 14.81% as D increases from 2.1 to 2.85. At initial dynamic loading, the instantaneous increase in axial stress reaches the crack initiation stress, significantly increasing the number of tensile cracks. As pre-static load increases, the model sample is subjected to a higher internal stress environment during dynamic loading, leading to more remarkable force chain breakage observed at peak strength. Shear failure, including oblique shear failure and tensile-shear mixed failure, is the primary failure mode under static-dynamic combined loading. The additional constraints provided by bolts increase strain energy stored in particles and contacts and reduce the crack number at peak strength, with the constraining effect exhibiting more pronounced as preload increases. For anchored samples, the end of pallets is the initiation point for shear cracks, which extend along the edge of the preload concentration area, while tensile cracks initiating from the sample ends propagate toward the preload concentration area.

Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surfaces Empowered Cooperative Rate Splitting with User Relaying.

In this work, we unveil the advantages of synergizing cooperative rate splitting (CRS) with user relaying and simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR RIS). Specifically, we propose a novel STAR RIS-assisted CRS transmission framework, featuring six unique transmission modes that leverage various combinations of the relaying protocols (including full duplex-FD and half duplex-HD) and the STAR RIS configuration protocols (including energy splitting-ES, mode switching-MS, and time splitting-TS). With the objective of maximizing the minimum user rate, we then propose a unified successive convex approximation (SCA)-based alternative optimization (AO) algorithm to jointly optimize the transmit active beamforming, common rate allocation, STAR RIS passive beamforming, as well as time allocation (for HD or TS protocols) subject to the transmit power constraint at the base station (BS) and the law of energy conservation at the STAR RIS. To alleviate the computational burden, we further propose a low-complexity algorithm that incorporates a closed-form passive beamforming design. Numerical results show that our proposed framework significantly enhances user fairness compared with conventional CRS schemes without STAR RIS or other STAR RIS-empowered multiple access schemes. Moreover, the proposed low-complexity algorithm dramatically reduces the computational complexity while achieving very close performance to the AO method.